1. Field of the Invention
The present invention relates generally to a chain guide held in sliding contact with a chain for guiding the chain and, in particular, to a chain guide being capable of preventing excessive tightening and loosening of the chain during operation.
2. Description of the Related Art
Conventionally, chains have been used for transmitting rotation of a crankshaft of an engine to a camshaft. A typical example of such a chain is shown in FIG. 6 hereof. The chain 41 is trained around a drive sprocket 43 fixed to the crank-shaft 42 and a driven sprocket 45 fixed to the camshaft 44. A chain guide 46 is disposed between the drive sprocket 43 and the driven sprocket 45 and held in sliding contact with the chain 41 for preventing swinging of the chain upon running of the latter.
The chain guide 46 includes a shoe held in sliding contact with the chain 41. The chain guide 46 has one end secured to a mount surface of an engine (not shown) by means of a bolt 47 and an opposite end with an anchoring arm 48 secured to the mount surface of the engine by means of a bolt 50 passing through an oblong hole 49 formed in the anchoring arm 48.
After the conventional chain guide 46 is attached to the mount surface, it needs to be positionally fixed such that the chain 41 is not over tightened. However, such a position-fixing operation is difficult to achieve even when the oblong hole 49 is marked with a graduation for position adjustment, because the chain guide 46 has no means for preventing excessive tightening of the chain 41. Practically, to avoid loosening of the chain after assemblage, the chain guide 46 is fixed with the anchoring arm 48 pushed or forced toward the chain 41 to thereby tension the chain. This often results in fixing of the chain guide 46 with the chain 41 over tightened. The thus-over-tightened chain 41 poses a problem that it produces a whistling sound when driven. To avoid such over tightening of the chain, one may fix the anchoring arm 48 at a retracted position along the graduation. However, this will lead to another problem that unless the anchoring arm 48 is retracted a precisely appropriate amount, the chain becomes loose and hence produces flapping noises.